The measurement of PET images of an examination area typically requires measuring times in the range of minutes. As a result, moving body parts can only be measured out of focus. One possibility of improving the focus in the generated PET images resides in using the so-called gating. With cyclical movements such as for instance respiratory movement or heart movement, the overall measuring time available is divided into individual phases of the movement. In order to create the PET image, only the PET events which occur in a specific phase of the movement are taken into account. A sharp image, i.e. an image without motion artifacts, is herewith achieved. The price for this is however a reduced signal-to-noise ratio, since the measuring time per image is reduced. It is not necessary in many application instances to temporally resolve the movement of an organ in the examination area, but it is instead more important for instance to be able to identify a lesion in the organ. An image with an optimized signal-to-noise ratio is nevertheless required herefor. It can however only be achieved by lengthening the measuring time.